1. Field of the Invention
The present invention relates to a method of management and control of voice calls and a gateway used for that method.
In communication over conventional voice-based networks, voice information is transferred over a specific line switching route. A telephone switching network is a typical example of this.
This type of communication is optimal for applications requiring a real-time characteristic such as speech and is effective when the quality of speech is considered important.
On the other hand, as a network of a form different from a voice-based network such as a telephone switching network, there is a data-based network as represented by the Internet and intranets. Communication over a data-based network, as compared with communication over a voice-based network, is effective when thinking of importance to transmitting as large an amount of data as possible and to how to optimize transmission routes and increase efficiency. The most widely utilized network based on this method is the Internet Protocol (IP) network.
Up until now, voice-based networks and data-based networks have been operated by different communication methods from each other, but recently techniques for merging these communication methods have started to be established. For example, Voice over FR (VoFR), Voice over ATM (VoATM), and Voice over IP (VOIP) are well known as such techniques. Among these, VOIP is particularly attracting attention.
The reasons for this are that, first, the environment of the IP network has been improved due to the general spread of personal computers (PC) and application software and to the spread of the Internet using PCs and the application software and, second, communications costs have been greatly reduced through the integration of data and voice by IP networks.
Therefore, construction of VoIP-based unified networks is proceeding at a fast pace at the present time. Under the above circumstances, the present invention relates to a method for management and control of voice calls effective when applied to an IP network.
2. Description of the Related Art
As will be explained in detail later by using the drawings, during voice communication between a telephone set #1 and a telephone set #2 via a gateway over a dedicated line and a gateway of the other party, the problem arises that a real-time characteristic and a constant quality of speech can no longer be maintained since there is a time lag in the conversation or the conversation breaks up due to a delay of the voice call packets or packet loss and therefore a normal state of conversation cannot be achieved.
Usually, the emphasis in technical innovation in a unified network has been on how to use transmission lines more efficiently. An one example, a good state of communication over an IP network is being secured by band securing techniques such as RSVP (IntServ) or Diff Serv.
Depending on the network environment, however, there are many cases where the above band securing technique cannot be used. This is because all of the gateways, including routers, in the IP network have to have this band securing function. In the Internet etc., how and in what manner voice packets are routed is unknown. Therefore the above problem occurs.
Further, in VoIP-based communications, sometimes the communication is routed through a gatekeeper for managing calls. From the viewpoint of management of only voice calls, the state of the IP network can be monitored, but there are not many gatekeepers managing even data calls as well. Further, even if there were such a gatekeeper, communication using such a gatekeeper is not required in the standards and specifications, so the above problem again occurs.